1. Field of the Invention
The invention relates to a device for the controlled excision of a piece of tissue from a living body. The term "tissue," as used herein, refers, but is not limited to dense structures such as bone and other calcified structures and to soft structures such as solid organs and tumors. The tissue removed could be for the purpose of diagnosing a suspected pathologic condition that is involving the tissue, and/or for the purpose of completely removing all diseased tissue, thus effecting treatment of the disease. Another purpose of removing a piece of tissue would be to provide an access port to fluid or tissue below the surface of an organ or structure; the aspiration of marrow from the cavity of a bone is an example of this application of the invention.
2. Description of Prior or Contemporary Art
In the practice of clinical and research medicine, the practitioner is frequently required to remove a piece of tissue from an organ or structure that is suspected to be involved with a disease process. The tissue is then sent for microscopic examination and/or culture so that a diagnosis of the exact pathologic process can be made. At times, the entire area of suspected involvement is removed so that the disease process is not only diagnosed but is also definitively treated. Excision of diseased tissue may be performed through a surgical incision; the tissue then is excised under direct vision. Alternatively, the tissue may be excised by an instrument that is passed through a puncture wound in the skin and directed to the area of interest. This percutaneous technique eliminates the recovery period required after an open procedure. This in turn reduces the costs of the procedure as well as morbidity.
Three essential conditions must be satisfied by a device used to excise tissue: 1) The device must be controllable so that it does not deviate from the area of interest during the cutting process; 2) The depth of penetration must be displayed to the operator or controlled by a mechanical stop so that underlying structures deep to the area of interest are not damaged; 3) The sample of tissue cannot be crushed or otherwise damaged by the excision process which could result in an inaccurate pathologic diagnosis. A forth condition, required in specific applications, is continued access to the area where tissue has be removed. This would allow removal of additional tissue either by further excision or by aspiration. It would also permit application of a plug in the void at the excision site, thereby preventing hemorrhage or leakage of other bodily fluids.
There have been many prior art devices developed to remove tissue from a living body, some used during a surgical operation, others used percutaneously. Many of these devices utilize a narrow gauge hollow needle which is plunged into the area of interest and then withdrawn; a very small core of tissue is thus harvested. There are many variations to the "plunge type" instruments, but since none use a moving cutting edge, there use is limited to very soft tissue. A potential problem with these devices is that the architecture of the excised tissue may not be preserved due to compression of the specimen, even when used in soft tissue. Also, the depth of the tissue core cannot be monitored effectively.
U.S. Pat. No. 4,262,676 describes a bone biopsy device developed by Jamshidi that uses a hollow shaft cutter which is manually driven into the tissue using an oscillating rotational motion. A significant amount of pressure has to be maintained on the instrument to advance into the bone; when performing a biopsy on an irregularly shaped bone, the device may deviate laterally, and possibly completely slip off the surface. This can result in damage to surrounding structures or, minimally, not excising tissue from the precise area of interest. The device can only be used to excise a core from relatively soft cancellous bone. It does not incorporate a depth control feature.
There have many prior art devices developed to provide a more controlled excision of a core of hard tissue such as bone, some of which use a powered cutting cylinder. U.S. Pat. No. 4,306,570 describes a device used to excise hard tissue which features two counterrotating concentric cutting edges that are said to eliminate the problem of lateral migration as the cutting edges engage the tissue. The device neither has a depth control feature nor a means to allow for continued access to the area of excision after the core of tissue has been removed.
U.S. Pat. No. 3,893,445 describes a device for the biopsy of bone marrow which consists of a sheath device and a central cutting needle. The sheath is first positioned on the surface of the bone; a cutting cannula is then introduced through the sheath to excise a core of bone. The sheath does not substantially penetrate the bone and, therefore, one must maintain its position manually throughout the procedure in order to provide continued access to the tissue following removal of a core sample. No depth control feature is provided in this device.
U.S. Pat. No. 4,142,517 describes another instrument which uses a sheath that minimally penetrates the bone surface to prevent lateral deviation of a cutting shaft which is subsequently introduced. After the core is excised, the sheath may be driven into the bone as a separate operation, thus giving the operator continued access to the underlying tissue.